1. Field of the Invention
This invention relates to an optical disk drive for use with an optical disk for reading and/or writing information. More particularly this invention relates to an optical disk drive having a swing arm mounting for an optical unit for illuminating the optical disk.
2. Description of the Related Art
An optical disk drive reads and/or writes information consisting of characters, image data, audio data, or binary data on an optical disk with the use of a laser beam that is transmitted from a semiconductor laser.
As the optical disk drive employs a removable optical disk having a higher data storage capacity than other removable recording media, the disk drive is popularly used as an external storage unit, and is quickly becoming an indispensable part of an information processing apparatus. As the disk drive reads and/or writes information on a track formed concentrically or spirally on the optical disk, tracking of a small laser beam spot onto a desired track is required. As the spot is provided by focusing the laser beam with an objective lens mounted within an optical head, the spot can track a desired track by adjusting the position of the objective lens and by carrying the optical head to the desired location. It is necessarily to move the optical head back and forth in the radial direction of the optical disk over the range where the tracks are present in order to be able to access all of the tracks.
As the arrangement for carrying the optical head occupies a considerably large space in the disk drive, to make the arrangement smaller would permit miniaturization of the drive, which would increase the popularity of the disk drive.
There are two basic types of arrangements for carrying the optical head. In the first arrangement, the carriage carries the optical head back and forth in the linear direction. The first arrangement has been adopted for use in compact disk drives and CD-ROM drives, which each use the optical disk as a read-only memory for their associated computer system or other system. The first arrangement has a lead screw connected to a motor, and a ball-nut assembly connected to a carriage for mounting the optical head. Motor rotary motion is changed into the linear motion of the carriage by the lead screw and the ball-nut assembly. The linear motion tends to produce an energy loss resulting from frictional contact, and needs additional guide-parts for smooth and accurate motion of the carriage.
The second arrangement is called a swing arm type or a rotary arm type, which is, for example, described in U.S. Pat. No. 5,132,944, and is used for magneto-optical disk drives. The swing arm in U. S. Pat. No. 5,132,944 is supported at only a single portion thereof by a pivotable supporting assembly. As the driving unit includes a VCM (Voice Coil Motor) and an optical head, which are both mounted on the same side of the arm, the arm acts as a cantilever to support the weights of the VCM and the optical head. In this arrangement, preventing excess deflection of the arm normally requires increasing the stiffness of the arm, and often results in increasing the size of arm. Furthermore, smooth rotary motion of the arm usually requires a large sized pivotable supporting assembly for stiffening a shaft and a sleeve included within the assembly, as well as the use of ball bearings mounted within the assembly, in order to prevent frictional meshing caused by the biased load. Still more, it may be necessary to use a powerful driving unit, such as an expensive VCM, for smooth rotation of the arm while overcoming the frictional meshing. The use of the arm as a cantilever, such as in this arrangement, tends to increase the size and the cost of the disk drive.
Additionally, the larger the diameter of the optical disk is, the longer and heavier the arm needs to be, which then requires that the pivotable supporting assembly be of a larger size in order to prevent excessive deflection. In order to increase the popularity of the optical disk drive, a carriage arrangement suitable for small and low cost drives appears to be necessary.
An object of this invention is to provide an improved optical disk drive for use with an optical disk that includes a rotary motor, a swing arm for supporting an optical head to illuminate a laser beam onto the optical disk, and a supporting means. The supporting means supports the swing arm to pivotally move along a plane that is parallel to a surface of the optical disk. The swing arm is moved by the rotation of the motor, which is conveyed through a gear train consisting of a first toothed gear (which is mounted on the motor) and a second toothed gear (which is meshed with the first gear, and is mounted on an end of the arm).
In the present invention, as the arm is supported at two areasxe2x80x94the supporting means and the gear trainxe2x80x94the decreased load applied to the supporting means permits the use of a small and simple supporting means. Further, the decreased deflection of the arm allows the use of a small and lightweight arm. In addition to these advantages, a reduction ratio of the gear train allows for the use of a low output motor for driving the arm.
Other objects and advantages of the present invention will be apparent from the following description, the appended claims and accompanying drawings.